Process for producing coated detergent particles

ABSTRACT

A process for preparing detergent particles having a coating layer of water-soluble inorganic material is provided. The detergent particle comprises a particle core of a detergent active material. This particle core is then at least partially covered by a particle coating layer of a water soluble inorganic material. Particularly preferred are non-hydrate inorganic coating materials including double salt combinations of alkali metal carbonates, and sulfates. The particle coating layer may also include detergent adjunct ingredients such as brighteners, chelants, nonionic surfactants, co-builders, etc. The process includes the steps of passing the particle core through a coating mixer such as a low speed mixer of fluid bed mixer and coating the particle core with a coating solution or slurry of the water soluble inorganic material. Upon drying, the resultant detergent particles have improved appearance, flow properties, and improved solubility, and may be packaged and sold as a detergent material or mixed with various other detergent ingredients to provide a fully formulated detergent composition.

This application claims the benefit of Provisional application Ser. No.60/140,093, filed Jun. 21, 1999.

FIELD

The present invention relates to detergent particles and a process forproducing the particles. More particularly, the present inventionrelates to a process for producing coated detergent particles.

BACKGROUND

Recently, there has been considerable interest within the detergentindustry for laundry detergents which have the convenience, aestheticsand solubility of liquid laundry detergent products, but retain thecleaning performance and cost of granular detergent products. Theproblems, however, associated with past granular detergent compositionswith regard to aesthetics, solubility and user convenience areformidable. Such problems have been exacerbated by the advent of“compact” or low dosage granular detergent products which typically donot dissolve in washing solutions as well as their liquid laundrydetergent counterparts. These low dosage detergents are currently inhigh demand as they conserve resources and can be sold in small packageswhich are more convenient for consumers prior to use, but lessconvenient upon dispensing into the washing machine as compared toliquid laundry detergent which can be simply poured directly from thebottle as opposed to “scooped” from the box and then dispensed into thewashing solution.

As mentioned, such low dosage or “compact” detergent productsunfortunately experience dissolution problems, especially in coldtemperature laundering solutions (i.e., less than about 30° C.). Morespecifically, poor dissolution results in the formation of “clumps”which appear as solid white masses remaining in the washing machine oron the laundered clothes after conventional washing cycles. These“clumps” are especially prevalent under cold temperature washingconditions and/or when the order of addition to the washing machine islaundry detergent first, clothes second and water last (commonly knownas the “Reverse Order Of Addition” or “ROOA”). Such undesirable “clumps”are also formed if the consumer loads the washing machine in the orderof clothes, detergent and then water. Similarly, this clumpingphenomenon can contribute to the incomplete dispensing of detergent inwashing machines equipped with dispenser drawers or in other dispensingdevices, such as a granulette. In this case, the undesired result isundissolved detergent residue in the dispensing device.

It has been found that the cause of the aforementioned dissolutionproblem is associated with the “bridging” of a “gel-like” substancebetween surfactant-containing particles to form undesirable “clumps.”The gel-like substance responsible for the undesirable “bridging” ofparticles into “clumps” originates from the partial dissolution ofsurfactant in the aqueous laundering solutions, wherein such partialdissolution causes the formation of a viscous surfactant phase or pastewhich binds or otherwise “bridges” other surfactant-containing particlestogether into “clumps.” This undesirable dissolution phenomena iscommonly referred to as “lump-gel” formation. In addition to the viscoussurfactant “bridging” effect, inorganic salts have a tendency to hydratewhich can also cause “bridging” of particles which linked together viahydration. In particular, inorganic salts hydrate with one another toform a cage structure which exhibits poor dissolution and ultimatelyends up as a “clump” after the washing cycle. It would therefore bedesirable to have a detergent composition which does not experience thedissolution problems identified above so as to result in improvedcleaning performance.

The prior art is replete with disclosures addressing the dissolutionproblems associated with granular detergent compositions. For example,the prior art suggests limiting the use and manner of inorganic saltswhich can cause clumps via the “bridging” of hydrated salts during thelaundering cycle. Specific ratios of selected inorganic salts arecontemplated so as to minimize dissolution problems. Such a solution,however, constricts the formulation and process flexibility which arenecessary for current commercialization of large-scale detergentproducts. Various other mechanisms have been suggested by the prior art,all of which involve formulation alteration, and thereby reduceformulation flexibility. As a consequence, it would therefore bedesirable to have a process by which detergent compositions havingimproved dissolution without significantly inhibiting formulationflexibility can be produced.

Accordingly, the need remains for a process which can produce adetergent granule having improved flow properties and aesthetics, aswell as improved solubility, which may be included in detergentcompositions.

SUMMARY

This need is met by the present invention wherein a process forproducing a detergent particle that has improved surface, appearance,flow properties, and improved solubility is provided. The particles ofthe present invention have improved surface properties in that they aresmoother and have a generally more uniform surface and appearance thanprior art detergent particles. Further, the appearance of the particleshave been improved in that they appear brighter and whiter thancurrently available detergent particles and have improved flowproperties where the particles have reduced lumping and caking profiles.

In accordance with the present invention, a process for preparingdetergent compositions including granules having a coating layer of awater-soluble material is provided. The process comprises providingdetergent granules having at least one detergent active material andpassing those detergent granules through a coating mixer such as a lowspeed mixer or fluid bed mixer and coating the particle core with acoating solution or slurry of the water soluble coating material. Upondrying, the resultant detergent particles have improved appearance andflow properties and may be packaged and sold as a detergent material ormixed with various other detergent ingredients to provide a fullyformulated detergent composition.

The water soluble coating material is selected from the group consistingof detersive surfactants such as anionic surfactants, hydrotropes suchas sulfonates, polyethylene glycols and polypropylene glycols andmixtures thereof. In preferred embodiments, the coating material is amixture of an anionic surfactant and a hydrotrope in a ratio of anionicsurfactant to hydrotrope of from about 95:5 to about 5:95. Particularlypreferred are (a) a mixture of sodium linear alkyl benzene sulfonate,hydrophobic secondary alkyl sulfate, and/or sodium xylene sulfonate or(b) a mixture of sodium linear alkyl benzene sulfonate, hydrophobicsecondary alkyl sulfate, and/or disodium alkyldiphenyloxide disulfonate(commercially known as Dowfax hydrotrope with the alkyl group having achainlength from C1-C10), at a ratio of surfactants to hydrotrope offrom about 70:30 to about 95:5. Preferably, the amount of water-solublesolution is from about 1% to about 30%, by weight, of the detergentcomposition. Alternatively, coating material and thus the particlecoating layer may also include detergent adjunct ingredients such asbrighteners, chelants, nonionic surfactants, co-builders, etcincorporated into the coating.

In an optional embodiment of the present process, the process furthercomprises the steps of mixing the coated detergent granules with a flowcontrol aid to adhere the flow control aid to the surface of thegranules. The flow control aid is preferably an inorganic powdermaterial with a mean particle size of less than about 100 microns and isselected from the group consisting of crystalline layered silicate,carbonate, sodium sulfate, aluminosilicate, magnesium silicate, calciumsilicate, clay, and mixtures thereof.

Accordingly, it is an object of the present invention to provide aprocess for producing a detergent composition having improved appearanceand flow characteristics by coating detergent granules with a layer of awater soluble materials. It is a further object of the present inventionto provide a process for preparing the detergent particle via coating ina mixer with solutions or slurries of the inorganic materials. These andother objects features and advantages of the present invention willbecome apparent to those skilled in the art from a reading of thefollowing detailed description and the appended claims.

DETAILED DESCRIPTION Definitions

As used herein, the word “particles” means the entire size range of adetergent final product or component or the entire size range ofdiscrete particles, agglomerates, or granules in a final detergentproduct or component admixture. It specifically does not refer to a sizefraction (i.e., representing less than 100% of the entire size range) ofany of these types of particles unless the size fraction represents 100%of a discrete particle in an admixture of particles. For each type ofparticle component in an admixture, the entire size range of discreteparticles of that type have the same or substantially similarcomposition regardless of whether the particles are in contact withother particles. For agglomerated components, the agglomeratesthemselves are considered as discrete particles and each discreteparticle may be comprised of a composite of smaller primary particlesand binder compositions.

As used herein, the phrase “geometric mean particle diameter” means thegeometric mass median diameter of a set of discrete particles asmeasured by, any standard mass-based particle size measurementtechnique, preferably by dry sieving. As used herein, the phrase“geometric standard deviation” or “span” of a particle size distributionmeans the geometric breadth of the best-fitted log-normal function tothe above-mentioned particle size data which can be accomplished by theratio of the diameter of the 84.13 percentile divided by the diameter ofthe 50^(th) percentile of the cumulative distribution (Da_(84.13)/D₅₀);See Gotoh et al, Powder Technology Handbook, pp. 6-11, Marcel Dekker1997.

As used herein, the phrase “builder” means any inorganic material having“builder” performance in the detergency context, and specifically,organic or inorganic material capable of removing water hardness fromwashing solutions. As used herein, the term “bulk density” refers to theuncompressed, untapped powder bulk density, as measured by pouring anexcess of powder sample through a funnel into a smooth metal vessel(e.g., a 500 ml volume cylinder), scraping off the excess from the heapabove the rim of the vessel, measuring the remaining mass of powder anddividing the mass by the volume of the vessel.

As used herein, “composition” and “granular detergent composition” areintended to include both final products and additives/components of adetergent composition. That is, the compositions produced by theprocesses claimed herein may be complete laundry detergent compositionsor they may be additives that are used along with other detergentingredients for laundering fabrics and the like.

As used herein, “surface area” mean the total amount of surface of apowder available for gas adsorption and thus includes both internal(i.e. that within cracks and crevices) and external surface area.Surface area is measured using BET multi point surface area analysis.

The process of the present invention involves the production of coateddetergent granules for incorporation into a detergent composition Theprocess comprises in general, providing detergent granules. Thedetergent granules of the present invention comprise at least onedetergent active material and are preferably selected from spray-drieddetergent granules, wet detergent agglomerates, dry detergentagglomerates and dry detergent ingredients such as enzyme, bleach,perfumes, detergent adjunct ingredients or other granules typicallyincorporated into a detergent composition. The granules may be inparticle, agglomerate or flake form.

Detergent adjunct ingredients includes but is not limited to,carbonates, phosphates, sulfates, zeolites or the like. Of course, otherconventionally known ingredients may be included as well. Spray-drieddetergent granules include those particles which are manufactured via aconventional spray-drying technique wherein a slurry of detergentmaterials is prepared and, sprayed downward into a upwardly flowingstream of gas to dry the particles. A dry free flowing material isproduced from the process. Wet agglomerates include those particles thatare manufactured via a granulation type process wherein detergentadjunct ingredients such as described below are admixed with a liquidbinder material such as surfactant or a precursor thereof in at leastone mixer to form granules of detergent materials. These particles areknown as “wet agglomerates” until dried and as “dry agglomerates” uponexiting a drying stage, and optionally other conditioning stages such assizing, grinding and cooling. Binders include but are not limited towater, anionic surfactants and their precursors, nonionic surfactants,cationic surfactants, polyethylene glycol, polyvinyl pyrrolidone,polyacrylates, citric acid, and mixtures thereof.

Spray dried granules include those particles which are manufactured viaa conventional spray-drying technique wherein a slurry of detergentmaterials is prepared and sprayed downward into an upwardly flowingstream of gas to dry the particles. A dry, free flowing material isproduced from the process. For example, the slurry is passed to a towerwhere the slurry is sprayed into a stream of air at temperatures rangingfrom about 175° C. to about 450° C. to dry the detergent slurry and formdetergent particles. Typically, resultant densities of these particlesrange from about 200 to about 650 g/l.

Accordingly, the present invention entails the introduction of both rawmaterial or the introduction of previously formed detergent granules forcontinued processing of the granules. In a one preferred embodiment ofthe present invention, the granular feed stream comprises at least twoof the differing types of granules such as spray-dried granules and wetor dry detergent agglomerates. In one highly preferred embodiment, thefeed stream is comprised of spray-dried detergent granules, drydetergent agglomerates and detergent adjunct ingredients.

Detergent agglomerates of the present invention are typically formed byan agglomeration of a viscous surfactant paste or a liquid acidprecursor of a surfactant and the aforementioned detergent adjunctingredients. The agglomeration of the surfactant material and detergentadjunct material may be carried out in a coating mixer, such as a highor moderate speed mixer after which an optional low or moderate speedmixer may be employed for further agglomeration, if necessary.Alternatively, the agglomeration may be carried out in a single mixerthat can be low, moderate or high speed. The particular mixer used inthe present process should include pulverizing or grinding andagglomeration tools so that both techniques can be carried forthsimultaneously in a single mixer.

Residence times of the mixers will vary depending on the type of mixerand the operating parameters. For a preferred high-speed mixer, the meanresidence time is from about 0.1 to 60 seconds, more preferably fromabout 0.1 to about 30 seconds, even more preferably 0.1 to about 15seconds. Other preferred conditions of the high-speed mixer include fromabout 3 to 90 m/s of tip speed, and more preferably from about 10 to 70m/s of tip speed, and from about 0.005 W/kg to 100 W/kg of power draw,more preferably from about 0.05 W/kg to 80 W/kg of power draw.Preferably, if choppers are used, choppers can be used inside the mixerto break up undesirable oversized particles at an rpm of from about 0 to5000 rpm, more preferably from about 100 to 3000 rpm. Preferably, thewall temperature is from ambient to about 80° C. and the spacing betweenthe mixer elements and the wall is from about 0.1 cm to 25 cm. Examplesof a high-speed mixer having a mean residence time of from about 0.1 toabout 60 seconds are Lodige Recycler CB 30™, by Lodige Company, ormixers made by Drais, Schugi, or a similar brand mixer.

For a preferred moderate-speed mixer, the mean residence time is fromabout 30 to 1800 seconds, more preferably from about 30 to about 1200seconds, more preferably from about 30 to about 600 seconds. Otherpreferred conditions of the moderate-speed mixer include from about 0.1to 30 m/s of tip speed, and more preferably from about 1 to 25 m/s oftip speed, and from about 5 W/kg to 1000 W/kg of power draw, morepreferably from about 20 W/kg to 500 W/kg of power draw. Preferably, ifchoppers are used, choppers can be used inside the mixer to break upundesirable oversized particles at an rpm of from about 0 to 5000 rpm,more preferably from about 100 to 4000 rpm. Preferably, the walltemperature is from about −20° C. to about 80° C. and the spacingbetween the mixer elements and the wall is from about 0.1 cm to 25 cm.Examples of a moderate-speed mixer having a mean residence time of fromabout 30 to about 1800 seconds are Lodige Recycler KM “Ploughshare” 300™and 600™, by Lodige Company, the Drais K-T 160™ mixer, or mixers made byFukae. The Lodige KM “Ploughshare” 600™ moderate-speed mixer is aparticularly preferred mixer, which comprises a horizontal, hollowstatic cylinder having a centrally mounted rotating shaft around whichseveral plough-shaped blades are attached. Preferably, the shaft rotatesat a speed of from about 15 rpm to about 140 rpm, more preferably fromabout 80 rpm to about 120 rpm. In a preferred mixer, the grinding orpulverizing is accomplished by cutters, generally small r in size thatthe rotating shaft, which preferably operate at about 3600 rpm.

For a preferred low-speed mixer, the mean residence time is from about30 seconds to about 1800 seconds, more preferably from about 30 secondsto about 1200 seconds, and even more preferably from about 30 seconds toabout 600 seconds. The tip speed is preferably from about 0.1 m/s toabout 10 m/s, more preferably from about 0.2 m/s to about 7 m/s, andeven more preferably from about 0.2 m/s to about 3.5 m/s. Examples ofpreferred low-speed mixers include rotating bowl agglomerators, drumagglomerators, pan agglomerators, fluid bed granulators, and extruders.An example of an extruder is a multiple-screw extruder byWerner-Pfliedder (Germany).

In one preferred embodiment it has been found that the first processingstep can be successfully completed, under the process parametersdescribed, in a Lodige KM™ (Ploughshare) moderate speed mixer, LodigeCB™ high speed mixer, or mixers made by Fukae, Drais, Schugi or similarbrand mixer. The Lodige KM™ (Ploughshare) moderate speed mixer, which isa preferred mixer for use in the present invention, comprises ahorizontal, hollow static cylinder having a centrally mounted rotatingshaft around which several plough-shaped blades are attached. Othermixers similar in nature which are suitable for use in the processinclude the Lodige Ploughshare™ mixer and the Drais® K-T 160 mixer.

This agglomeration is typically followed by an optional drying step.This drying step may be carried out in a wide variety of equipmentincluding, but not limited to a fluid bed drying apparatus. Examples ofdryer characteristics include fixed or vibrating; rectangular bed orround bed; and straight or serpentine dryers. Manufacturers of suchdryers include Niro, Bepex, Spray Systems and Glatt. By way of example,apparatus such as a fluidized bed can be used for drying while anairlift can be used for cooling should it be necessary. The air lift canalso be used to force out the “fine” particles so that they can berecycled to the particle agglomeration process.

The agglomeration may comprise the step of spraying an additional binderin the mixers to facilitate production of the desired detergentparticles. A binder is added for purposes of enhancing agglomeration byproviding a “binding” or “sticking” agent for the detergent components.The binder is preferably selected from the group consisting of water,anionic surfactants, nonionic surfactants, polyethylene glycol,polyvinyl pyrrolidone polyacrylates, citric acid and mixtures thereof.Other suitable binder materials including those listed herein aredescribed in Beerse et al, U.S. Pat. No. 5,108,646 (Procter & GambleCo.), the disclosure of which is incorporated herein by reference.

Another optional processing step to form the particle core of thepresent invention includes continuously adding a coating agent such aszeolites, recycled “fines” as described above and fumed silica to themixer to improve the particle color, increase the particle “whiteness orfacilitate free flowability of the resulting detergent particles and toprevent over agglomeration. When employing recycled fines as the coatingagent, the fines are preferably in the approximate size range of 0.1 to0.9 times the mean particle size of the larger particles. The particlecoating layer will also improve the integrity of the fines layering andprovide abrasion and attrition resistance during handling. In addition,the detergent starting materials can be fed into a pre-mixer, such as aLodige CB mixer or a twin-screw extruder, prior to entering in themixer. This step, although optional, does indeed facilitateagglomeration.

The particles of the present invention comprise at least about 50% byweight of particles having a geometric mean particle diameter of fromabout 400 microns to about 1500 microns and preferably have a geometricstandard deviation of from about 1 to about 2. Preferably the geometricstandard deviation is from about 1.0 to about 1.7, preferably from about1.0 to about 1.4. The granular detergent composition resulting from theprocesses may comprise undersized or fine particles, wherein “fineparticles” are defined as particles that have a geometric mean particlediameter that is less than about 1.65 standard deviations below thechosen geometric mean particle diameter of the granular detergentcomposition at a given geometric standard deviation. Oversized or largeparticles may also exist wherein “large particles” are defined asparticles that have a geometric mean particle diameter that is greaterthan about 1.65 standard deviations above the chosen geometric meanparticle diameter of the granular detergent composition at a givengeometric standard deviation. The fine particles are preferablyseparated from the granular detergent composition and returned to theprocess by adding them to at least one of the mixers and/or the fluidbed dryer as described in detail below. Likewise, the large particlesare preferably separated from the granular detergent composition andthen fed to a grinder where their geometric mean particle diameter isreduced. After the geometric mean particle diameter of the largeparticles is reduced, the large particles are returned to the process byadding them to at least one of the mixers and/or the fluid bed dryer.

Particle Coating Layer

As described hereinbefore, detergent compositions of the presentinvention comprises granules that have been at least partially coatedwith a water soluble coating material thereby forming a water solublecoating layer on the granules. The particle coating layer impartsdramatically new surface and appearance properties on the granules ofthe present invention. The coated granules of the present invention havean appearance which is brighter and/or whiter than current detergentparticles. This provides a more favorable response from consumers whoprefer white detergent products.

Most importantly, the coated particles of the present invention provideimproved clumping and flowability profiles to detergent productscontaining the particles of the present invention. The particle coatinglayer provides a coating which is crisper and non-tacky. While effectiveat improving flowability in all detergent products, it is particularlyeffective at preventing clumping in products containing surfactantswhich are more difficult to dry to a non-tacky state including nonionicsurfactants, linear alkyl benzene sulfonates (“LAS”), and ethoxylatedalkyl sulfates or in detergent products containing high amounts ofsurfactant actives (i.e. greater than about 25 wt % surfactant active).

The particle coating layer of the present invention at least partiallycoats the granule. While the desired state is for granules which arecompletely coated by the particle coating, it is, of course, anticipatedthat complete coverage will not be possible in all cases in acontinuous, high speed manufacturing process. While it is ratherdifficult to quantify the extent of the coating layer coverage, it isobserved that increasing the amount of coating solids, either byincreasing the solids concentration in the solution or by spraying onmore of the solution, results in improved benefits and the appearance ofa more uniform coverage. The benefits of increased coverage is balancedwith the cost of drying excess water in the process. Accordingly, inpreferred embodiments of the present invention, adequate coverage isachieved by applying coating solids at more than about 1 wt. % and mostpreferably more than about 5 wt. % of the uncoated granule mass or in anamount of from about 1% to about 30% by weight of the finished detergentcomposition.

The particle coating layer of the present invention comprises a watersoluble coating material. In preferred embodiments the coating materialis selected from the group consisting of detersive surfactants such asanionic surfactants, hydrotropes and mixtures thereof

The hydrotropes of the present invention are preferably selected fromsulfonates salts such as alkali metal sulfonates in particular sodiumxylene sulfonate, sodium toluene sulfonate, sodium cumene sulfonate,disodium alkyldiphenyloxide disulfonate (commercially known as Dowfaxhydrotrope with the alkyl group having a chainlength from C1-C10),hydrophobic secondary alkyl sulfate, and sodium3,5-diisopropylbenzenesulfonate; polyethylene glycols having a molecularweight of from about 200 to about 8000 and polypropylene glycols havinga molecular weight of from about 200 to about 8000. When hydrotropes areemployed as the coating material the hydrotrope is preferably present inan amount of from about 1% to about 20%, more preferably about 2% toabout 15% and most preferably about 3% to about 10% by weight of thefinished detergent composition.

The surfactants of the present invention may include anionic, nonionic,zwitterionic, ampholytic and cationic classes and compatible mixturesthereof. Detergent surfactants are described in U.S. Pat. No. 3,664,961,Norris, issued May 23, 1972, and in U.S. Pat. No. 3,919,678, Laughlin etal., issued Dec. 30, 1975, both of which are incorporated herein byreference. Cationic surfactants include those described in U.S. Pat. No.4,222,905, Cockrell, issued Sep. 16, 1980, and in U.S. Pat. No.4,239,659, Murphy, issued Dec. 16, 1980, both of which are alsoincorporated herein by reference.

Nonlimiting examples of surfactant for use in the coating of the presentinvention include the conventional C₁₁-C₁₈ alkyl benzene sulfonates(“LAS”) and primary, branched-chain and random C₁₀-C₂₀ alkyl sulfates(“AS”), the C₁₀-C₁₈ secondary (2,3) alkyl sulfates of the formulaCH₃(CH₂)_(x)(CHOSO₃ ⁻M⁺) CH₃ and CH₃ (CH₂)_(y)(CHOSO₃ ⁻M⁺) CH₂CH₃ wherex and (y+1) are integers of at least about 7, preferably at least about9, and M is a water-solubilizing cation, especially sodium, unsaturatedsulfates such as oleyl sulfate, the C₁₀-C₁₈ alkyl alkoxy sulfates(“AE_(x)S”; especially EO 1-7 ethoxy sulfates), C₁₀-C₁₈ alkyl alkoxycarboxylates (especially the EO 1-5 ethoxycarboxylates), the C₁₀₋₁₈glycerol ethers, the C₁₀-C₁₈ alkyl polyglycosides and theircorresponding sulfated polyglycosides, and C₁₂-C₁₈ alpha-sulfonatedfatty acid esters. If desired, the conventional nonionic and amphotericsurfactants such as the C₁₂-C₁₈ alkyl ethoxylates (“AE”) including theso-called narrow peaked alkyl; ethoxylates and C₆-C₁₂ alkyl phenolalkoxylates (especially ethoxylates and mixed ethoxy/propoxy), C₁₂-C₁₈betaines and sulfobetaines (“sultaines”), C₁₀-C₁₈ amine oxides, and thelike, can also be included in the surfactant system. The C₁₀-C₁₈ N-alkylpolyhydroxy fatty acid amides can also be used. Typical examples includethe C₁₂-C₁₈ N-methylglucamides. See WO 9,206,154. Other sugar-derivedsurfactants include the N-alkoxy polyhydroxy fatty acid amides, such asC₁₀-C₁₈ N-(3-methoxypropyl) glucamide. The N-propyl through N-hexylC₁₂-C₁₈ glucamides can be used for low sudsing. C₁₀-C₂₀ conventionalsoaps may also be used. Hydrophobic secondary alkyl sulfates are alsopreferred. When surfactants are employed as the coating material, thesurfactant is preferably present in an amount of from about 1% to about30%, more preferably about 3% to about 20% and most preferably about 5%to about 10% by weight of the finished detergent composition.

In preferred embodiments, the coating material comprises a mixture ofanionic surfactants and hydrotropes. Ratios of the surfactant tohydrotrope preferably from about 95:5 to about 5:95 and more preferablyrange from about 90:10 to about 10:90. When mixtures are employed as thecoating material, the mixture is preferably present in an amount of fromabout 1% to about 30%, more preferably about 3% to about 20% and mostpreferably about 3% to about 15% by weight of the finished detergentcomposition. Particularly preferred are (a) a mixture of sodium linearalkyl benzene sulfonate and/or hydrophobic secondary alkyl sulfate andsodium xylene sulfonate or (b) a mixture of sodium linear alkyl benzenesulfonate, hydrophobic secondary alkyl sulfate, and/or disodiumalkyldiphenyloxide disulfonate (commercially known as Dowfax hydrotropewith the alkyl group having a chainlength from C1-C10), at a ratio offrom surfactant to hydrotrope from about 70:30 to about 95:5. Thepreferred viscosity range for the coating solution or slurry duringapplication ranges from about 50 to about 100,000 centipoise, morepreferably from about 100 to about 50,000 cp, and most preferably fromabout 300 to about 30,000 cp at 60 deg.C.

The particle coating layer may also include an detergent supplement inaddition to the particle coating material. These detergent supplementmay include a wide variety of ingredients, including but not limited tooptical brighteners, pigments or dyes, chelants, nonionic surfactants,pH control agents, detergency co-builders, fillers and mixtures of thesematerials. Particularly preferred are pigments or dyes such as titaniumdioxide, bluing agents such as copper sulfate, zinc thiosulfate andUltramarine blue, Sparkle enhancers such as mica flake, fillers such assodium carbonate and sodium sulfate and co-builders such as citrates andnonionic surfactants.

The granules of the present invention are produced by coating thegranules as described hereinbefore with the particle coating material ina coating mixer. The coating mixer may be any of a number of mixersincluding high, moderate, and low speed mixers such as a Lodige KM™(Ploughshare) moderate speed mixer, Lodige CB™ high speed mixer, ormixers made by Fukae, Drais, Schugi or similar brand mixer, as describedin detail above. Particularly preferred for use in the present inventionare low speed drum mixers and low shear fluidized bed mixers. Whenemploying a low speed drum mixer in the present invention, the mixer ispreferably followed in sequence by a drying apparatus, for example afluid bed or air lift, wherein the coated particles are then dried toachieve the coated particles of the present invention. The drying step,however, is optional.

In a preferred embodiment of the present invention, the coating mixer isa fluidized bed, or is used in combination with any of the mixersdescribed above. In one preferred embodiment, the distribution ofcoating between the mixer and fluid beds can be in a ratio of 100:0 to5:95. The preferred granules of detergent agglomerates, spray-driedgranules or most preferably mixtures thereof is passed into a fluid beddryer having multiple internal “stages” or “zones”. A stage or zone isany discrete area within the dryer, and these terms are, usedinterchangeably herein. The process conditions within a stage may bedifferent or similar to the other stages in the dryer. It is understoodthat two adjacent dryers are equivalent to a single dryer havingmultiple stages. The various feed streams of granules and coatingmaterial can be added at the different stages, depending on, forexample, the particle size and moisture level of the feed stream.Feeding different streams to different stages can minimize the heat loadon the dryer, and optimize the particle size and shape as definedherein.

Typically, the fluid bed mixer of the present invention comprises afirst coating zone where the particle coating material of the presentinvention is applied. The coating zone involves the spraying of thecoating material in aqueous or slurry form onto the fluidized particles.The bed is typically fluidized with heated air in order to dry orpartially dry moisture from the spray coating as it is applied. Thespraying is achieved via nozzles capable of delivering a fine oratomized spray of the coating mixture to achieve complete coverage ofthe particles. Typically, the droplet size from the atomizer is lessthan about 2 times the particle size. This atomization can be achievedeither through a conventional two-fluid nozzle with atomizing air, oralternatively by means of a conventional pressure nozzle. To achievethis type of atomization, the solution or slurry theology is typicallycharacterized by a viscosity of less than about 500 centipoise,preferably less than about 200 centipoise. While the nozzle location inthe fluid bed may be in most any location, the preferred location is apositioning that allows a vertical down spray of the coating mixturesuch as a top spray configuration. To achieve best results, the nozzlelocation is placed at or above the fluidized height of the particles inthe fluid bed. The fluidized height is typically determined by a weir oroverflow gate height. The coating zone of the fluid bed is thentypically followed by a drying zone and a cooling zone. Of course, oneof ordinary skill in the art will recognize that alternativearrangements are also possible to achieve the resultant coated particlesof the present invention.

Typical conditions within a fluid bed or agitated fluid bed apparatus ofthe present invention include (I) from about 1 to about 20 minutes ofmean residence time, (ii) from about 100 to about 1200 mm of depth ofunfluidized bed from the fluid bed plate or from 0 to about 600 mm fromthe top of fluid bed, (iii) a droplet size of less than 2 times theparticle size preferably not more than about 100 micron of droplet spraysize, more preferable not more than 50 micron, (iv) from about 150 toabout 1600 mm of spray height, (v) from about 0.4 to about 4.0 m/s offluidizing velocity and (vi) from about 12 to about 200° C. of bedtemperature, preferably from about 12 to about 150° C., and even morepreferably from about 12 to 100° C. Once again, one of ordinary skill inthe art will recognize that the conditions in the fluid bed may varydepending on a number of factors.

The coated granules exiting the coating mixer may comprise in and ofthemselves a fully formulated detergent composition or in preferredembodiments may be admixed with additional ingredients, such asbleaching agents, enzymes, perfumes, non-coated detergent particles, andvarious other ingredients to produce a fully formulated detergentcomposition.

The coated granular detergent composition of the present inventionachieves the desired benefits of solubility, improved aesthetics andflowability via the process of the present invention and the control orselection of the geometric mean particle diameter of certain levels ofparticles in the composition. By “improved aesthetics”, it is meant thatthe consumer prefers a granular detergent product which has a moreuniform appearance of particles as opposed to past granular detergentproducts which contained particles of varying size and composition. Tothat end, at least about 50%, more preferably at least about 75%, evenmore preferably at least about 90%, and most preferably at least about95/by weight of the total particles in the detergent product, have theselected mean particle size diameter. In this way, a substantial portionof the granular detergent product will have the uniform size so as toprovide the aesthetic appearance desired by consumers.

Preferably, the geometric mean particle diameter of the particles isfrom about 400 microns to about 1500 microns, more preferably from about600 microns to about 1200 microns, and most preferably from about 600microns;to about 1000 microns. The particle size distribution is definedby a relative tight geometric standard deviation or “span” so as not tohave too many particles outside of the target size. Accordingly, thegeometric standard deviation is preferably is from about 1 to about 2,more preferably is from about 1.0 to about 1.7, even more preferably isfrom about 1.0 to about 1.4, and most preferably is from about 1.0 toabout 1.2. As can be recognized by one of ordinary skill in the art, thecontrol of improperly sized particles via the present inventioncontributes to the tight span of the composition produced by the presentinvention.

While not intending to be bound by theory, it is believed thatsolubility is enhanced as a result of the particles in the detergentcomposition being more of the same size. Specifically, as a result ofthe particles being more uniform in size, the actual “contact points”among the particles in the detergent composition is reduced which, inturn, reduces the “bridging effect” commonly associated with the“lump-gel” dissolution difficulties of granular detergent compositions.Previous granular detergent compositions contained particles of varyingsizes which leads to more contact points among the particles. Forexample, a large particle could have many smaller particles in contactwith it rendering the particle site ripe for lump-gel formation. Thelevel and uniform size of the particles in the granular detergentcomposition of the present invention avoids such problems.

By “a portion” of the particles, it is meant that at least someparticles in the detergent composition contain a detersive surfactantand/or a detergent builder to provide the fundamental building blocks ofa typical detergent composition. The various surfactants and builders aswell as their respective levels in the composition are set forthhereinafter. Typically, the detergent composition will, contain fromabout 1% to about 50% by weight of a detersive surfactant and from about1% to about 75% by weight of a detergent builder.

A particularly important attribute of detergent powders is color. Coloris usually measured on a Hunter Colorimeter and reported as threeparameters “L”, “a” and “b”. Of particular relevance to the powdereddetergent consumer is the whiteness of the powder determined by theequation L-3b. In general, whiteness values below about 60% areconsidered poor. Whiteness can be improved by a number of means such asfor example including a pigment or whitening agent in the coating layerof the granules such as titanium dioxide.

Another important attribute of the granular detergent products of thisinvention is the shape of the individual particles. Shape can bemeasured in a number of different ways known to those of ordinary skillin the art. One such method is using optical microscopy with Optimus(V5.0) image analysis software. Important calculated parameters are:

“Circularity” which is defined as (measured perimeter length of theparticle image)²/(measured area of the particle image). The circularityof a perfectly smooth sphere (minimum circularity) is 12.57; and

“Aspect Ratio” which is defined as the length/width of the particleimage.

Each of these attributes is important and can be averaged over the bulkgranular detergent composition. And the combination of the twoparameters as defined by the product of the parameters is important aswell (i.e. both must be controlled to get a product with goodappearance). Preferably, the granular detergent compositions produced bythe process of the present invention have circularities less than about50, preferably less than about 30, more preferably less than about 23,most preferably less than about 18. Also preferred are granulardetergent compositions with aspect ratios less than about 2, preferablyless than about 1.5, more preferably less than about 1.3 most preferablyless than about 1.2.

Additionally, it is preferred to have a uniform distribution of shapesamong the particles in the composition. Specifically, the granulardetergent compositions of this invention have a standard deviation ofthe number distribution of circularity less than about 20, that ispreferably less than about 10, more preferably less than about 7 mostpreferably less than about 4. And the standard deviation of the numberdistribution of aspect ratios is preferably less than about 1, morepreferably less than about 0.5, even more preferably less than about0.3, most preferably less than about 0.2.

In an especially preferred process of the present invention, granulardetergent compositions are produced wherein the product of circularityand aspect ratio is less than about 100, preferably less than about 50,more preferably less than about 30, and most preferably less than about20. Also preferred are granular detergent compositions with the standarddeviation of the number distribution of the product of circularity andaspect ratio of less than about 45, preferably less than about 20, morepreferably less than about 7 most preferably less than about 2.

As previously stated, the coated particles of the present invention haveimproved surface properties in that the particles are more uniform inshape and smoother on the surface than the uncoated spray-dried oragglomerated detergent particles. These features are reflected in areduction of the overall surface area of particles having the coating ofthe present invention as opposed to particles not having the coatings ofthe present invention. The coatings of the present invention reducetotal surface area by smoothing irregularities and filling crevices onthe surface of the particles. The coatings of the present inventionprovide a reduction in overall surface area as measured by the formula:

(Surface Area of Non-Coated Particles)−(Surface Area of CoatedParticles)/(Surface Area of Non-Coated Particles)*100=Percent of SurfaceArea Reduction

of at least about 10%, more preferably at least about 20% and mostpreferably at least about 30%. A reduction in surface area as providedby the present invention leads to improved flow properties and toimproved overall aesthetics by providing a more reflective surface.

Surface Area Test Method

The surface area of the particles of the present invention are measuredaccording to the following procedure. Detergent Particles are placedinto a Micromeritics VacPrep 061, available from Micromeritics ofNorcross, Georgia, for pre-test preparation. The particles are placedunder a vacuum of approximately 500 millitorr and heated to atemperature of between 80 and 100° C. for approximately 16 hours. TheBET multi-point surface area is then measured in a Micromeritics Gemini2375 surface area analyzer using a mixture of helium and nitrogen gasesand the following general conditions: Evacuation rate—500.0 mmHg/min;Analysis Mode—Equilibration; Evacuation Time—1.0 min.; SaturationPressure—771.77 mmHg; Equilibration Time—5 sec. Helium/NitrogenPressure—15 psig; Helium and Nitrogen purity 99.9%, free space ismeasured and P/Po points cover 0.05 to 0.3 with 5 data points taken.

The preferred detergent compositions of this invention meet at least oneand most preferably all, of the attribute measurements and standarddeviations as defined above, that is for whiteness, color uniformitycircularity, percent surface area reduction and aspect ratio.

In an optional embodiment of the present invention, the coated particlesof the present invention may be treated with a post coating glosstreatment to provide a gloss layer on the coated detergent particle. Thegloss layer may comprise inorganic salt materials, chelating materials,polymeric materials and mixtures thereof. Preferred inorganic materialsare sulfate salts such as magnesium sulfate, preferred chelants arediamines such as ethylene diamine disuccinic acids (EDDS), whilepreferred polymers include acrylic polymers and copolymers such asacrylic/maleic copolymers.

Detergents Components

Fully formulated detergent compositions of the present invention mayinclude any number of conventional detergent ingredients. For example,the surfactant system of the detergent composition may include anionic,nonionic, zwitterionic, ampholytic and cationic classes and compatiblemixtures thereof. Detergent surfactants are described in U.S. Pat. No.3,664,961, Norris, issued May 23, 1972, and in U.S. Pat No. 3,919,678,Laughlin et al., issued Dec. 30, 1975, both of which are incorporatedherein by reference. Cationic surfactants include those described inU.S. Pat. No. 4,222,905, Cockrell, issued Sep. 16, 1980, and in U.S.Pat. No. 4,239,659, Murphy, issued Dec. 16, 1980, both of which are alsoincorporated herein by reference.

Nonlimiting examples of surfactant systems include the conventionalC₁₁-C₁₈ alkyl benzene sulfonates (“LAS”) and primary, branched-chain andrandom C₁₀-C₂₀ alkyl sulfates (“AS”), the C₁₀-C₁₈ secondary (2,3) alkylsulfates of the formula CH₃(CH₂)_(x)(CHOSO₃ ⁻M⁺) CH₃ and CH₃(CH₂)_(y)(CHOSO₃ ⁻M⁺) CH₂CH₃ where x and (y+1) are integers of at leastabout 7, preferably at least about 9, and M is a water-solubilizingcation, especially sodium, unsaturated sulfates such as oleyl sulfate,the C₁₀-C₁₈ alkyl alkoxy sulfates (“AE_(x)S”; especially EO 1-7 ethoxysulfates). C₁₀-C₁₈ alkyl alkoxy carboxylates (especially the EO 1-5ethoxycarboxylates), the C₁₀₋₁₈ glycerol ethers, the C₁₀-C₁₈ alkylpolyglycosides and their corresponding sulfated polyglycosides, andC₁₂-C₁₈ alpha-sulfonated fatty acid esters. If desired, the conventionalnonionic and amphoteric surfactants such as the C₁₂-C₁₈ alkylethoxylates (“AE”) including the so-called narrow peaked alkylethoxylates and C₆-C₁₂ alkyl phenol alkoxylates (especially ethoxylatesand mixed ethoxy/propoxy), C₁₂-C₁₈ betaines and sulfobetaines(“sultaines”), C₁₀-C₁₈ amine oxides, and the like, can also be includedin the surfactant system. The C₁₀-C₁₈ N-alkyl polyhydroxy fatty acidamides can also be used. Typical examples include the C₁₂-C₁₈N-methylglucamides. See WO 9,206,154. Other sugar-derived surfactantsinclude the N-alkoxy polyhydroxy fatty acid amides, such as C₁₀-C₁N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C₁₂-C₁₈glucamides can be used for low sudsing. C₁₀-C₂₀ conventional soaps mayalso be used. If high sudsing is desired, the branched-chain C₁₀-C₁₆soaps may be used. Mixtures of anionic and nonionic surfactants areespecially useful. Other conventional useful surfactants are listed instandard texts.

The detergent composition can, and preferably does, include a detergentbuilder. Builders are generally selected from the various water-soluble,alkali metal, ammonium or substituted ammonium phosphates,polyphosphates, phosphonates, polyphosphonates, carbonates, silicates,borates, polyhydroxy sulfonates, polyacetates, carboxylates, andpolycarboxylates. Preferred are the alkali metal, especially sodium,salts of the above. Preferred for use herein are the phosphates,carbonates, silicates, C₁₀₋₁₈ fatty adds, polycarboxylates, and mixturesthereof. More preferred are sodium tripolyphosphate, tetrasodiumpyrophosphate, citrate, tartrate mono- and di-succinates, sodiumsilicate, and mixtures thereof (see below).

Specific examples of inorganic phosphate builders are sodium andpotassium tripolyphosphate, pyrophosphate, polymeric metaphosphatehaving a degree of polymerization of from about 6 to 21, andorthophosphates. Examples of polyphosphonate builders are the sodium andpotassium salts of ethylene diphosphonic acid, the sodium and potassiumsalts of ethane 1-hydroxy-1,1-diphosphonic acid and the sodium andpotassium salts of ethane, 1,1,2-triphosphonic acid. Other phosphorusbuilder compounds are disclosed in U.S. Pat. Nos. 3,159,581; 3,213,030;3,422,021; 3,422,137; 3,400,176 and 3,400,148, all of which areincorporated herein by reference.

Examples of nonphosphorus, inorganic builders are sodium and potassiumcarbonate, bicarbonate, sesquicarbonate, tetraborate decahydrate, andsilicates having a weight ratio of SiO₂ to alkali metal oxide of fromabout 0.5 to about 4.0, preferably from about 1.0 to about 2.4.Water-soluble, nonphosphorus organic builders useful herein include thevarious alkali metal, ammonium and substituted ammonium polyacetates,carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples ofpolyacetate and polycarboxylate builders are the sodium, potassium,lithium, ammonium and substituted ammonium salts of ethylene diaminetetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, melliticacid, benzene polycarboxylic adds, and citric acid.

Polymeric polycarboxylate builders are set forth in U.S. Pat. No.3,308,067, Diehl, issued Mar. 7, 1967, the disclosure of which isincorporated herein by reference. Such materials include thewater-soluble salts of homo- and copolymers of aliphatic carboxylicacids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid,aconitic acid, citraconic acid and methylenemalonic acid. Some of thesematerials are useful as the water-soluble anionic polymer as hereinafterdescribed, but only if in intimate admixture with the nonsoap anionicsurfactant.

Other suitable polycarboxylates for use herein are the polyacetalcarboxylates described in U.S. Pat. No. 4,144,226, issued Mar. 13, 1979to Crutchfield et al., and U.S. Pat. No. 4,246,495, issued Mar. 27, 1979to Crutchfield et al., both of which are incorporated herein byreference. These polyacetal carboxylates can be prepared by bringingtogether under polymerization conditions an ester of glyoxylic acid anda polymerization initiator. The resulting polyacetal carboxylate esteris then attached to chemically stable end groups to stabilize thepolyacetal carboxylate against rapid depolymerization in alkalinesolution, converted to the corresponding salt, and added to a detergentcomposition. Particularly preferred polycarboxylate builders are theether carboxylate builder compositions comprising a combination oftartrate monosuccinate and tartrate disuccinate described in U.S. Pat.No. 4,663,071, Bush et al., issued May 5, 1987, the disclosure of whichis incorporated herein by reference.

Water-soluble silicate solids represented by the formula SiO₂.M₂O, Mbeing an alkali metal, and having a SiO₂:M₂O weight ratio of from about0.5 to about 4.0, are useful salts in the detergent granules of theinvention at levels of from about 2% to about 15% on an anhydrous weightbasis, preferably from about 3% to about 8%. Anhydrous or hydratedparticulate silicate can be utilized, as well.

Any number of additional ingredients can also be included as componentsin the granular detergent composition. These include other detergencybuilders, bleaches, bleach activators, suds boosters or sudssuppressors, ant-tarnish and anti-corrosion agents, soil suspendingagents, soil release agents, germicides, pH adjusting agents, nonbuilderalkalinity sources, chelating agents, smectite clays, enzymes,enzyme-stabilizing agents and perfumes. See U.S. Pat. No. 3,936,537,issued Feb. 3, 1976 to Baskerville, Jr. et al., incorporated herein byreference.

Bleaching agents and activators are described in U.S. Pat. No.4,412,934, Chung et al., issued Nov. 1, 1983, and in U.S. Pat. No.4,483.781, Hartman, issued Nov. 20, 1984, both of which are incorporatedherein by reference. Chelating agents are also described in U.S. Pat.No. 4,663,071, Bush et al., from Column 17, line 54 through Column 18,line 68, incorporated herein by reference. Suds modifiers are alsooptional ingredients and are described in U.S. Pat. No. 3,933,672,issued Jan. 20, 1976 to Bartoletta et al., and 4,136,045, issued Jan.23, 1979 to Gault et al., both incorporated herein by reference.

Suitable smectite clays for use herein are described in U.S. Pat. No.4,762,645, Tucker et al., issued Aug. 9, 1988, Column 6, line 3 throughColumn 7, line 24, incorporated herein by reference. Suitable additionaldetergency builders for use herein are enumerated in the Baskervillepatent, Column 13, line 54 through Column 16, line 16, and in U.S. Pat.No. 4,663,071, Bush et al., issued May 5, 1987, both incorporated hereinby reference.

The following examples are presented for illustrative purposes only andare not to be construed as limiting the scope of the appended claims inany way.

EXAMPLES

In the following examples all levels are quoted as % by weight of thecomposition:

Example I

A detergent composition having base granules of the following formula isproduced via a conventional spray drying process:

NaLAS 29.58 NaAS 5.23 Cationic (CocoK3) 1.51 ML-9 13.80 Sodium silicate2R 15.06 Brighteners 0.35 Sodium carbonate 20.67 Zeolite A 4.43Miscellaneous 5.62 Moisture 3.75 Total 100.00

The spray-dried granules are compacted in a roll compactor at 60-110bars compaction pressure and the resultant compacted sheet is ground ina cage mill or Fitz mill. The compacted and ground particles are thencoated with a surfactant containing coating medium in a moderate-speedmixer (KM-600™). The average residence time is 5 minutes and thesurfactant containing paste is added at 60 deg.C. A Tulip type ofchopper is used in the mixer to disperse the coating medium and to chopany lumps formed during the coating process. A coated detergentcomposition having the following formula is obtained:

A B C D Base granule 79.69 77.39 75.55 77.17 Coating Material 60% activepaste¹ — 6.01 — — 51% total active mixture (90/10) — — 7.56 — paste² 40%active solution³ — — — 5.80 20% Sodium sulfate solution 2.02 — — —Zeolite on Coated Granules 6.70 5.01 6.35 6.49 Bleach activator (NOBS)4.00 4.00 4.00 4.00 Coated Sodium Percarbonate 4.50 4.50 4.50 4.50 SoilRelease Polymers 0.34 0.34 0.34 0.34 Suds suppressor 1.00 1.00 1.00 1.00Layered sodium silicate 1.05 1.05 — — Protease enzyme 0.50 0.50 0.500.50 Perfume 0.20 0.20 0.20 0.20 Total 100.00 100.00 100.00 100.00¹sodium linear alkyl benzene sulfonate ²sodium linear alkyl benzenesulfonate and sodium xylene sulfonate ³sodium xylene sulfonate ordisodium alkyldiphenyloxide disulfonate (commercially known as Dowfaxhydrotrope with the alkyl group having a chainlength from C1-C10)

In all the examples that follow, the spray-dried granule is comprised of11% surfactant, 74% inorganic salts, 5% polyacrylate polymer, 5% soap,and 5% moisture. The dry agglomerate composition is comprised of 30%surfactant, 62% inorganic salts, 4% sodium aluminosilicate, and 4%moisture. The following are examples of processes for obtainingdust-free high density granules with narrower particle sizedistribution, improved flowability and better solubility. The resultingcoated composition has a geometric mean particle diameter of from about400 to 1500 microns with a geometric standard deviation of from about 1to about 2, unless otherwise indicated.

Example II

Step 1

360 kgs/hr of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) and 360 kgs/her of a dry agglomerate (particle sizeof 450 microns, bulk density of 780 g/l) is introduced into amoderate-speed mixer KM-600™ Lodige Mixer with 8 serrated ploughs and 4christmas-tree choppers mounted perpendicular to the ploughs along thelength of the mixer. The mixer is divided into four zones. The gapbetween the ploughs and the wall of the mixer is about 3 cms. The walltemperature is maintained at 30° C.

Step 2

105-115 kgs/hr of aqueous linear alkyl benzene sulphonate paste(C11-C18, 60% active) is dispersed by the first chopper into the mixerand 70 kgs/hr of crystalline sodium aluminosilicate is added in the lastzone of the mixer. The surfactant paste is fed at 50° C. and the powdersare fed at room temperature. The condition of the moderate-speed mixerKM-600 is as follows:

Mean residence time: 7.5-10 minutes

Tip Speed: 2-3 m/s

Power Draw: 20-500 W/kg

Chopper RPM: 3600

The resulting granules have a bulk density of 750-850 g/l. The geometricmean particle size diameter is 450 microns.

Example III

Step 1

800 grams of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) is premixed for 2 minutes in a Processal™Tilt-a-plow bench-scale Mixer with total volume of 4 litres. This mixeris equipped with standard ploughs and one tulip-shaped chopperbottom-mounted in the centre of the mixer.

Step 2

200 grams of aqueous linear alkyl benzene sulphonate paste (C11-C18, 60%active) is injected into the mixer and dispersed with the action of thechopper blades on the powders over a period of 5 minutes. The paste isat 50° C. and the powders are at room temperature.

Step 3

After the paste is added, mixing is continued for 2.5 minutes and then100 grams of crystalline sodium alumino-silicate is added into themixer. Mixer Operating Conditions are as follows:

Total batch time: 15 minutes

Tip Speed: 0.5-1 m/s

Chopper RPM: 3600

After mixing further for 3 minutes, the contents are fed into afluidized bed for drying. The inlet air temperature is 105° C., airvelocity is 0.6 m/s and drying time is 5 minutes.

The resulting granules have a bulk density of 750-850 g/l. The geometricmean particle diameter is 500 microns.

Example IV

Step 1

360 kgs/hr of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) and 360 kgs/her of a dry agglomerate (particle sizeof 450 microns, bulk density of 780 g/l) is introduced into a high-speedSchugi Mixer. 40 kgph of aqueous linear alkyl benzene sulphonate paste(C11-18, 30% active) is sprayed on the powders using a SU 26 two-fluidnozzle (air pressure: 1-5 kg/cm², liquid pressure: 2-3 kg/cm²). Theliquid is sprayed on at 50° C. and the powders are at room temperature.The operating conditions of the high-speed Schugi Mixer are as follows:

Tip Speed: 24 m/s

Mean residence Time: 0.1-1 second

Power Draw: 1-5 kW/kg

Step 2

The output from the Schugi is fed into a moderate-speed mixer KM-600™Mixer and 60 kgph of aqueous linear alkyl benzene sulphonate paste(C11-C18, 60% active) is dispersed by the first chopper into themoderate-speed mixer and 70 kgs/hr of crystalline sodium aluminosilicateis added in the last zone of the mixer. The surfactant paste is fed at50° C. The condition of the moderate-speed mixer

KM-600 is as follows:

Mean residence time: 2-3 minutes

Tip Speed: 2-3 m/s

Power Draw: 20-500 W/kg

Chopper RPM: 3600

Step 3

The product from the moderate-speed mixer KM-600™ is subjected toconditioning operations of gas-fluidized bed drying, gas-fluidized bedcooling and sizing. The inlet air temperature in the dryer is 120° C.and the air velocity is 1 m/s. Inlet air humidity in the dryer is 10%.The inlet air temperature in the cooler is 10° C., the air velocity is 1m/s and the inlet air humidity is 40%.

The resulting granules have a bulk density of 750-850 g/l.

Example V

Step 1

360 kgs/hr of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) and 360 kgs/her of a dry agglomerate (particle sizeof 450 microns, bulk density of 780 g/l) is introduced into a high-speedSchugi Mixer. 40 kgph of aqueous linear alkyl benzene sulphonate paste(C11-18, 30% active) is sprayed on the powders using a SU 26 two-fluidnozzle (air pressure: 1-5 kg/cm², liquid pressure: 2-3 kg/cm²). Theliquid is sprayed on at 50° C. and the powders are at room temperature.The operating conditions of the Schugi Mixer are as follows:

Tip Speed: 24 m/s

Mean residence Time: 0.1-1 second

Power Draw: 1-5 kW/kg

Step 2

The output from the Schugi is fed into a moderate-speed mixer KM-600™and 40 kgph of aqueous linear alkyl benzene sulphonate paste (C11-C18,60% active) is dispersed by the first chopper into the moderate-speedmixer and 50 kgs/hr of crystalline sodium aluminosilicate is added inthe last zone of the mixer. The surfactant paste is fed at 50° C. Thecondition of the moderate-speed mixer KM-600™ is as follows:

Mean residence time: 2-3 minutes

Tip Speed: 2-3 m/s

Power Draw: 20-500 W/kg

Chopper RPM: 3600

Step 3

The product from the moderate-speed mixer KM-600™ is fed into a secondhigh-speed Schugi Mixer. 20 kgph of aqueous polyethylene glycol solution(mol.wt.:4000, 40% active) is sprayed on the powders using a SU 26two-fluid nozzle (air pressure: 1-5 kg/cm², liquid pressure: 2-3kg/cm²). The liquid is sprayed on at 50° C. The operating conditions ofthe Schugi Mixer are as follows:

Tip Speed: 24 m/s

Mean residence Time: 0.1-1 second

Power Draw: 1-5 kW/kg

Step 4

The output from the Schugi is subjected to conditioning operations ofgas-fluidized bed drying, gas-fluidized bed cooling and sizing. Theinlet air temperature in the dryer is 120° C. and the air velocity is 1m/s. Inlet air humidity in the dryer is 10%. The inlet air temperaturein the cooler is 10° C., the air velocity is 1 m/s and the inlet airhumidity is 40%.

The resulting granules have a bulk density of 750-850 g/l.

Example VI

Step 1

360 kgs/hr of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) and 360 kgs/her of a dry agglomerate (particle sizeof 450 microns, bulk density of 780 g/l) is introduced into amoderate-speed mixer KM-600™. 60 kgph of aqueous linear alkyl benzenesulphonate paste (C11-C18, 60% active) is dispersed by the first chopperinto the mixer and 50 kgs/hr of crystalline sodium aluminosilicate isadded in the last zone of the mixer. The surfactant paste is fed at 50°C. and the powders are at room temperature. The condition of themoderate-speed mixer KM-600™ is as follows:

Mean residence time: 2-3 minutes

Tip Speed: 2-3 m/s

Power Draw: 20-500 W/kg

Chopper RPM: 3600

Step 2

The output from the moderate-speed mixer KM-600™ is fed into ahigh-speed Schugi and 40 kgph of aqueous polyethylene glycol solution(mol.wt.:4000, 40% active) is sprayed on the powders using a SU 26two-fluid nozzle (air pressure: 1-5 kg/cm², liquid pressure: 2-3kg/cm²). The liquid is sprayed on at 50° C. The operating conditions ofthe high-speed Schugi Mixer are as follows:

Tip Speed: 24 m/s

Mean residence Time: 0.1-1 second

Power Draw: 1-5 kW/kg

Step 3

The product from the Schugi is subjected to conditioning operations ofgas-fluidized bed drying, gas-fluidized bed cooling and sizing. Theinlet air temperature in the dryer is 120° C. and the air velocity is 1m/s. Inlet air humidity in the dryer is 10%. The inlet air temperaturein the cooler is 10° C., the air velocity is 1 m/s and the inlet airhumidity is 40%.

The resulting granules have a bulk density of 750-850 g/l.

Example VII

Step 1

360 kgs/hr of a spray-dried granule (particle size of 400 microns, bulkdensity of 400 g/l) and 360 kgs/her of a dry agglomerate (particle sizeof 450 microns, bulk density of 780 g/l) is introduced into amoderate-speed KM-600™ Lodige Mixer with 8 serrated ploughs and 4christmas-tree choppers mounted perpendicular to the ploughs along thelength of the mixer. The mixer is divided into four zones. The gapbetween the ploughs and the wall of the mixer is about 3 cms. The walltemperature is maintained at 30° C.

Step 2

105-115 kgs/hr of aqueous C16-C17 branched alkyl sulphate/C14C15 linearalkyl sulphate paste (ratio of 60:40, 50% active) is dispersed by thefirst chopper into the mixer and 70 kgs/hr of crystalline sodiumaluminosilicate is added in the last zone of the mixer. The surfactantpaste is fed at 50° C. and the powders are fed at room temperature. Thecondition of the KM-600™ mixer is as follows:

Mean residence time: 7.5-10 minutes

Tip Speed: 2-3 m/s

Power Draw: 20-500 W/kg

Chopper RPM: 3600

Step 3

The product from the KM-600™ is subjected to conditioning operations ofgas-fluidized bed drying, gas-fluidized bed cooling and sizing. Theinlet air temperature in the dryer is 120° C. and the air velocity is 1m/s. Inlet air humidity in the dryer is 10%. The inlet air temperaturein the cooler is 10° C., the air velocity is 1 m/s and the inlet airhumidity is 40%.

Having thus described the invention in detail, it will be obvious tothose skilled in the art that various changes may be made withoutdeparting from the scope of the invention and the invention is not to beconsidered limited to what is described in the specification.

What is claimed is:
 1. A process for preparing a coated granulardetergent composition comprising the steps of: i) providing a granulardetergent composition having granules containing detergent activematerials; ii) passing said detergent granules to a coating mixer; iii)providing a coating solution of a water soluble coating material,wherein the water soluble coating material is a mixture of an anionicsurfactant and a hydrotrope, wherein a) the anionic surfactant isselected from the group consisting of sodium linear alkyl benzenesulfonate, hydrophobic secondary alkyl sulfate mixture thereof; b) thehydrotrope is selected from the group consisting of sodium xylenesulfonate, alkyldiphenyloxide disulfonate having alkyl group chainlength of from C1-C10, and mixture thereof; and c) the ratio ofsurfactant to hydrotrope is from about 70:30 to about 95:5; and iv) atleast partially coating said granules in said coating mixer to form acoated detergent granular composition; wherein said coated detergentcomposition has a geometric mean particle diameter of from about 400microns to about 1500 micorons with a geometric standard deviation offrom about 1 to about
 2. 2. The process as claimed in claim 1 whereinsaid coating mixer is selected from the group consisting of low speedmixers, fluid bed mixers, and combinations thereof.
 3. The process asclaimed in claim 1 wherein said coating materials further includes adetergent supplements such as brighteners, chelants, nonionicsurfactants, co-builders and mixtures thereof.
 4. The process as claimedin claim 1 wherein said step of providing said aqueous coating solutionfurther comprises the step of spraying said coating solution into saidcoating mixer.
 5. The process as claimed in claim 4 wherein the amountof coating solution is from about 1% to about 30%, by weight, of thedetergent composition.
 6. The process as claimed in claim 1 furthercomprising the steps of mixing said coated detergent granules with aflow control aid to adhere said flow control aid to the surface of saidgranules.
 7. The process as claimed in claim 6 wherein the flow controlaid is an inorganic powder material and is selected from the groupconsisting of crystalline layered silicate, carbonate, sodium sulfate,aluminosilicate, magnesium silicate, calcium silicate, clay, andmixtures thereof.
 8. A granular detergent composition produced by theprocess of claim
 1. 9. A process for preparing a coated granulardetergent composition comprising the steps of: i) providing a granulardetergent composition having granules containing detergent activematerials; ii) passing said detergent granules to a coating mixer; iii)providing a coating solution of a water soluble coating material,wherein the water soluble coating material is a mixture of an anionicsurface and a hydrotrope, wherein a) the anionic surfactant is selectedfrom the group consisting of sodium linear alkyl benzene sulfonate,hydrophobic secondary alkyl sulfate and mixtures thereof; and b) thehydrotrope is selected from the group consisting of sodium xylenesulfonate, alkyldiphenyloxide disulfonate having an alkyl chain lengthof from C1-10, and mixtures thereof; and c) the ratio of surfactant tohydrotrope is from about 70:30 to about 95:5 and iv) at least partiallycoating said granules in said coating mixer to form a coated detergentgranular composition.
 10. The process as claimed in claim 9, whereinsaid coating mixer is selected from the group consisting of low speedmixers, fluid bed mixers, and combinations thereof.
 11. The process asclaimed in claim 9 further comprising the steps of mixing said coateddetergent granules with a flow control aid to adhere said flow controlaid to the surface of said granules.
 12. The process as claimed in claim11 wherein the flow control aid is an inorganic powder material and isselected from the group consisting of crystalline layered silicate,carbonate, sodium sulfate, aluminosilicate, magnesium silicate, calciumsilicate, clay, undersized detergent particles and mixtures thereof. 13.A granular detergent composition produced by the process of claim 9.